//2009/08/28 11:38:50
#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <queue>
#include <sstream>
#include <algorithm>

using namespace std;

class FallingFactorialPower
{
public:
    double compute(int n, int k)
    {
        if (k>0)
        {
            double ret = 1.0;
            for (int i=0; i<k; i++)
                ret *= 1.0 * (n-i);
            return ret;
        }
        else
        {
            double ret = 1.0;
            for (int i=1; i<=abs(k); i++)
                ret /= 1.0 * (n+i);
            return ret;
        }
    }
};
